A human basal body temperature represents a body temperature measured in a resting state in which a factor of a change in a body temperature caused by activity is eliminated and only a minimum energy required for life support is consumed. In the case of women, the basal body temperature is closely related to an ovulation cycle. For this reason, the basal body temperature is utilized for various purposes, for example, reference of a woman who desires pregnancy or nonpregnancy, analysis of the cause of irregular menstruation or observation of progress thereof, and the like. Recently, the basal body temperature is utilized for a beauty, regulation of a health condition or the like in some cases.
Usually, the basal body temperature of a woman is changed periodically between approximately 0.3 to 0.5 degree except for the case of a sickness or heavy stress. By measuring the basal body temperature every day to know a rhythm (a change in a body temperature), it is possible to grasp a condition of a body such as presence of ovulation, a period of menstruation or a period likely to get pregnant.
It is necessary to accurately capture a fine change in a value. For this reason, the basal body temperature is usually measured in a body resting state. As a specific measuring method, it is recommended to perform measurement in a state in which a user is lying down in bed when a body has not been moved and an inner part of the body is taking a rest immediately after waking with enough sleeping.
Conventionally, there is proposed the technique for starting various sensors in a timing five minutes before a set time of an alarm clock (a standard time required for measuring a body temperature by a temperature sensor), deciding by these sensors whether the user is trying to measure a basal body temperature, and giving warning if there is a possibility that the measurement might be forgot (for example, see Patent Document 1).
According to the technique described in the Patent Document 1, the user can be promoted to measure the basal body temperature without forgetting it immediately after waking. Referring to the technique described in the Patent Document 1, however, the user measures the basal body temperature after the user is forcibly waken through an alarm clock or receives the warning from a device. For this reason, the measurement cannot be performed in a resting state.
On the other hand, there is also proposed the technique for going to bed with a body temperature measuring device attached to a housing pocket in underwear and measuring a basal body temperature and recording the basal body temperature in a memory during sleeping (for example, see Patent Document 2). The Patent Document 2 also describes that the sleep onset of a user is confirmed by the acceleration sensor and the measurement of a body temperature is then started by the temperature measuring element. According to the technique described in the Patent Document 2, it is possible to measure a basal body temperature in a resting state during sleeping.
Patent Document 1: Japanese Laid-Open Patent Publication No. 2012-220287
Patent Document 2: Japanese Laid-Open Patent Publication No. 2005-164405